Expression of immunoreactivities to 75 kDa nerve growth factor receptor, trk gene product and phosphotyrosine in granular cell tumors.

Nineteen granular cell tumors (GCT) of adults, two congenital granular cell epulides and five epulides fibrosae were immunohistochemically examined to detect the expression of 75 kDa nerve growth factor receptor (NGFR), trk gene product, phosphotyrosine (PT), protein gene product 9.5 (PGP9.5) and S-100 protein. The NGFR-immunoreactivity (IR) and trk gene product-IR were expressed on almost all granular cells of GCT. PT-IR was also demonstrated on granular cells of all GCT examined, although the frequency of positive cells was low. Congenital granular cell epulides and epulides fibrosae were negative for NGFR-IR, trk gene product-IR and PT-IR. S-100 protein was localized in granular cells of adult GCT but not in the granular cells of congenital epulis. On the other hand, PGP9.5 was detected in granular cells of both conditions and in fibroblastic cells of epulis fibrosa. The present results further indicate that GCT is of peripheral nerve Schwann cell origin, while the congenital granular cell epulides are not of neural origin. NGFR and trk gene product expressed on GCT seems to be functional in terms of phosphorylation of the tyrosine residue in the receptor or downstream protein in signal transduction.